52Mbps, Precision Delay, RS485 Fail-Safe Transceiver

The LTC1685 is a high speed, precision delay RS485 transceiver that can operate at data rates as high as 52Mbps. The device also meets the requirements of RS422.

A unique architecture provides very stable propagation delays and low skew over a wide common mode and ambient temperature range.

The driver and receiver feature three-state outputs, with disabled driver outputs maintaining high impedance over the entire common mode range. A short circuit feature detects shorted outputs and substantially reduces driver output current. A similar feature also protects the receiver output from short circuits. Thermal shutdown circuitry protects from excessive power dissipation.

The receiver has a fail-safe feature that guarantees a high output state when the inputs are shorted or are left floating. The LTC1685 RS485 transceiver guarantees receiver fail-safe operation over the entire common mode range (–7V to 12V). Input resistance will remain ≥22k when the device is unpowered or disabled.

The LTC1685 operates from a single 5V supply and draws only 7mA of supply current.

Applications

* High Speed RS485/RS422 Transceivers

* Level Translator

* Backplane Transceiver

* STS-1/OC-1 Data Transceiver

* Fast-20, Fast-40 SCSI Transceivers

* Precision Propagation Delay Over Temperature:

* Receiver/Driver: 18.5ns ±3.5ns

* High Data Rate: 52Mbps

* Low tPLH/tPHL Skew:

* Receiver/Driver: 500ps Typ

* –7V to 12V RS485 Input Common Mode Range

* Guaranteed Fail-Safe Receiver Operation Over the Entire Common Mode Range

* High Receiver Input Resistance: ≥22k, Even When Unpowered

* Short-Circuit Protected

* Thermal Shutdown Protected

* Driver Maintains High Impedance in Three-State or with Power Off

* Single 5V Supply

* Pin Compatible with LTC485

* 45dB CMRR at 26MHz